Caldicellulosiruptor bescii DSM 6725 (formerly Anaerocellum thermophilum, Yang et al. 2009, hit J Syst Evol Microbiol 60:2011-2015) grows at temperatures up to about 90° C. and is the most thermophilic cellulolytic bacterium known. This obligate anaerobe is capable of degrading lignocellulosic biomass including hardwood (e.g., poplar) and grasses with both low lignin (e.g., napier grass and beiniuda grass) and high lignin (e.g., switchgrass) content without chemical pretreatment (Yang et al., 2009 Appl Environ Microbiol 75:4762-4769). When grown on crystalline cellulose, it produces lactate, ethanol, acetate, H2, and CO2 (Svetlichnyi et al., 1990 Mikrobiologiya 59:598-604). Its genome includes sequences encoding cellulases, glycoside hydrolases, pectinases, pullulanases, and transporters that are important in biomass deconstruction (Kataeva et al., 2009 J Bacteriol 191:3760-3761). This variety of cellulolytic enzymes and end products, in combination with an optimal growth temperature near 80° C. make C. bescii an important microorganism not only in the study of biomass deconstruction, but also in the industrial development of ethanol and other biofuels. This genus has many advantages for consolidated bioprocessing (CBP) and offers the possibility for production of bioenergy and bioproducts from lignocellulosic biomass by a single organism in a single step fermentation (Lynd et al., 2002 Microbiol Mol Biol Rev 66:506-577).